CN109182810B - Low-cost high-room-temperature plastic deformation magnesium alloy and preparation method thereof - Google Patents

Low-cost high-room-temperature plastic deformation magnesium alloy and preparation method thereof Download PDF

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CN109182810B
CN109182810B CN201811375906.6A CN201811375906A CN109182810B CN 109182810 B CN109182810 B CN 109182810B CN 201811375906 A CN201811375906 A CN 201811375906A CN 109182810 B CN109182810 B CN 109182810B
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magnesium alloy
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CN109182810A (en
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孟帅举
韩海生
李其智
张士良
余晖
闻晶晶
范少达
李永胜
赵维民
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Beijing Zhong'an Jingrun New Material Technology Co ltd
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Hebei University of Technology
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    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C23/00—Alloys based on magnesium
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C1/00—Making non-ferrous alloys
    • C22C1/02—Making non-ferrous alloys by melting
    • C22C1/03—Making non-ferrous alloys by melting using master alloys
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C1/00—Making non-ferrous alloys
    • C22C1/06—Making non-ferrous alloys with the use of special agents for refining or deoxidising
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22F—CHANGING THE PHYSICAL STRUCTURE OF NON-FERROUS METALS AND NON-FERROUS ALLOYS
    • C22F1/00—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working
    • C22F1/002—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working by rapid cooling or quenching; cooling agents used therefor
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22F—CHANGING THE PHYSICAL STRUCTURE OF NON-FERROUS METALS AND NON-FERROUS ALLOYS
    • C22F1/00—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working
    • C22F1/06—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working of magnesium or alloys based thereon

Abstract

The invention relates to a low-cost high-room temperature plastic deformation magnesium alloy and a preparation method thereof. The alloy is Mg-Bi-Sn-Zr-Ca-Y alloy, and comprises the following chemical components in percentage by mass: 2-5.0 wt% of Bi; 2-5.0 wt% of Sn; 0.5-1.2 wt% of Zr; 0.1-0.8 wt% of Ca; 0.01 to 0.08 wt% of Y, and the balance of Mg and inevitable impurities; and, the mass ratio Bi: ca is 6-7: 1. The invention can obtain the wrought magnesium alloy with high room temperature plasticity by using an extremely simple processing means, the room temperature elongation of the wrought magnesium alloy reaches more than 35 percent, and meanwhile, the raw materials and the processing cost are low, and the mass production is easy to realize.

Description

Low-cost high-room-temperature plastic deformation magnesium alloy and preparation method thereof
Technical Field
The invention relates to the field of metal materials and metal material processing, in particular to a low-cost high-room-temperature plastic deformation magnesium alloy and a preparation method thereof; the novel magnesium alloy can be used as a potential heat-resistant magnesium alloy and a biomedical magnesium alloy material.
Background
Energy, materials and information are three major pillars for the development of human society, and energy conservation is reducedThe situation is increasingly severe, and the development and utilization of light magnesium-based materials rich in resources are a necessary trend. The magnesium density is about 1.74g/cm3The material is about 2/3 of aluminum alloy, 1/4 of steel, and the magnesium alloy has a series of advantages of small density, high specific strength and specific stiffness, good electromagnetic shielding effect, good damping and shock absorption and the like, is known as a green metal engineering material in twenty-first century, and has wide application prospect in the fields of aerospace, electronic communication, transportation and the like. At present, from the global demand and research and development conditions of magnesium alloys, the development and research work of magnesium alloys mainly develops towards high-strength magnesium alloys, high-plasticity magnesium alloys, heat-resistant magnesium alloys, fiber or particle reinforced magnesium matrix composites and the like.
However, in the development of high plasticity magnesium alloys, the crystal structure of magnesium and most of the alloys is hexagonal close packing, and the low temperature (< 220 ℃) condition can start the slip system to a small extent, so that the room temperature plasticity is poor. The cylindrical surface sliding system and the conical surface sliding system can be started only at a higher temperature, so that the plasticity of the magnesium alloy is improved. However, in the processing process of magnesium alloy, too high temperature often causes coarsening of magnesium alloy grains, deteriorates the mechanical properties of the alloy, and simultaneously, the working procedures of heating, heat preservation and the like also increase the processing cost of the alloy. Therefore, the development of the magnesium alloy with excellent plasticity at room temperature or lower temperature is beneficial to realizing the plastic processing of the magnesium alloy at low temperature or even at room temperature, further avoiding the deterioration of alloy structure, improving the product performance, simultaneously reducing the cost of energy consumption and the like caused by blank heating in the further processing process, and greatly promoting the wide application of the magnesium alloy as a novel green material in the fields of automobiles, rail transit, aviation and the like.
In recent years, with the increasing demand for lightweight transportation vehicles, a great deal of research has been conducted to prepare high-room-temperature plastic magnesium alloys by various methods, and some high-room-temperature plastic magnesium alloys are developed at home and abroad. Patent 1 (application publication number: CN1616697C) discloses a high-plasticity magnesium alloy containing rare earth yttrium, which consists of Mg, Zn, Zr and Y, and comprises the following components in percentage by mass: 5.0 to 8.5 percent; zr: 0.6 to 0.8 percent; y0.7-2.0%, the balance being magnesium and unavoidable impurities. After extrusion processing, the elongation of the alloy at room temperature can reach 18.37-21.45%, and the whole plasticity is still low. Patent 2 (application publication number: CN102925771A) discloses a high room temperature plastic magnesium alloy material and a preparation method thereof: according to the mass percent of Li: 1.0-5.0%, Al: 2.5-3.5%, Zn: 0.7-1.3%, Mn: 0.2-0.5%, less than or equal to 0.3% of impurities and the balance of magnesium. The alloy is prepared by vacuumizing a pure lithium and AZ31 magnesium alloy and smelting the pure lithium and AZ31 magnesium alloy under the condition of introducing inert gas, and the elongation of the alloy at room temperature is 14-31%. The alloy smelting process is complex, and the whole room temperature elongation is still low. Patent 3 (application publication No. CN102061414A) discloses a high-plasticity magnesium alloy and a preparation method thereof, which comprises the following components: al: 0.5-2%, Mn: 2%, Ca: 0.02-0.1 percent, and the balance of magnesium, and the elongation at room temperature can reach 25 percent. The alloy of the invention has lower cost, but the elongation is still low as a whole.
These prior inventions, or the preparation process has higher requirements on production conditions, or contains more noble metal elements such as rare earth elements, and the like, which directly or indirectly increase the alloy cost, and most alloys still have low room temperature plasticity.
In order to better meet the requirements of industries such as consumer electronics and automobiles on low cost, easy processing and high performance of the high-strength magnesium alloy, the magnesium alloy material which does not contain rare earth or contains trace rare earth and has low cost and high room temperature plasticity is urgently needed to be developed and can be prepared by a simple production and processing process so as to be directly used or used as a blank for further low-temperature plastic processing to improve the alloy performance, thereby promoting the further popularization and application of the magnesium alloy.
Disclosure of Invention
Aiming at the problems that the room temperature plasticity of the existing high room temperature plasticity magnesium alloy is not high enough, or a plurality of rare earth elements and high-valence alloy elements are used in large quantity or the processing technology requirement is strict, so that the cost is overhigh, and the like, the low-cost high room temperature plasticity deformation magnesium alloy and the preparation method thereof are provided. The alloy is a novel Mg-Bi-Sn-Zr-Ca-Y alloy, Sn element is introduced on the basis of the Mg-Bi alloy, and multielement and microscale composite alloying is carried out on the Sn element and trace Zr, Ca and Y elements, and the proportion of the Bi element and the Ca element is controlled at the same time, so that the Mg-Bi-Sn-Zr-Ca-Y alloy is prevented from being used for carrying out the multielement and microscale composite alloying2Ca phase is generated to avoid the deterioration of the plasticity of the alloy. System for makingIn the preparation method, the invention needs to be carried out at a higher temperature (750 ℃) in the smelting process, the casting process does not need protection gas protection, and the casting can be directly carried out in the atmosphere. The invention can obtain the wrought magnesium alloy with high room temperature plasticity by using an extremely simple processing means, the room temperature elongation of the wrought magnesium alloy reaches more than 35 percent, and meanwhile, the raw materials and the processing cost are low, and the mass production is easy to realize.
The technical scheme of the invention is as follows:
the low-cost high-room-temperature plastic deformation magnesium alloy is Mg-Bi-Sn-Zr-Ca-Y alloy and comprises the following chemical components in percentage by mass: 2-5.0 wt% of Bi; 2-5.0 wt% of Sn; 0.5-1.2 wt% of Zr; 0.1-0.8 wt% of Ca; 0.01 to 0.08 wt% of Y, and the balance of Mg and inevitable impurities; and, the mass ratio Bi: ca is 6-7: 1.
The preparation method of the low-cost high-room-temperature plastic deformation magnesium alloy comprises the following steps of:
1) preparing materials: taking pure Mg ingot, pure Bi block, pure Sn block, Mg-Zr intermediate alloy, Mg-Ca intermediate alloy and Mg-Y intermediate alloy as raw materials, and batching according to the components of the magnesium alloy;
2) smelting: putting a pure Mg ingot into a crucible of a smelting furnace, setting the furnace temperature to 700-730 ℃ and keeping the furnace temperature, and after the pure Mg ingot is melted, respectively adding a pure Bi block and a pure Sn block which are preheated to 50-80 ℃, and a Mg-Zr intermediate alloy, a Mg-Ca intermediate alloy and a Mg-Y intermediate alloy which are preheated to 100-150 ℃ into a magnesium solution; then raising the melting temperature to 750-780 ℃, preserving the heat for 10-30 minutes until the alloy is molten, stirring for 3-10 minutes, and introducing high-purity Ar gas into the melt for refining and degassing treatment; regulating and controlling the temperature to 750-760 ℃, and keeping the temperature and standing for 3-10 minutes; the smelting and the heat preservation standing processes are both in CO2/SF6Under the protection of mixed gas;
3) casting: pouring the magnesium alloy melt after standing into a mold preheated to 200-250 ℃ to prepare as-cast magnesium alloy; gas protection is not needed in the casting process;
4) solid solution: carrying out solid solution treatment on the obtained as-cast magnesium alloy, wherein the solid solution treatment temperature is 460-500 ℃ and the time is 8-12 hours, and then quenching with warm water at the temperature of 30-80 ℃; gas protection is not needed in the heating and heat preservation processes of the solution treatment;
5) cutting the cast ingot subjected to the solution treatment obtained in the previous step into corresponding blanks and peeling;
6) extrusion deformation: heating the blank obtained in the previous step to 270-400 ℃ within 20-30 minutes, and then putting the blank into a die for deformation processing; and air cooling is carried out after the deformation processing, and finally the magnesium alloy material with low cost and high room temperature plastic deformation is obtained.
The mould is used for forming rods, plates, pipes, wires or profiles.
The stirring in the step 2) is mechanical stirring or argon-blowing stirring.
The Mg-Zr intermediate alloy is preferably Mg-30Zr intermediate alloy.
The Mg-Ca master alloy is Mg-20Ca master alloy.
The Mg-Y master alloy is Mg-30Y master alloy.
Said CO2And SF6The mixed gas of (A) is composed of CO in a volume ratio2：SF6＝50～100：1。
The invention has the substantive characteristics that:
the plasticity of magnesium alloy is closely related to the grain size, the type, size, quantity, distribution of the second phase and the texture configuration in the alloy.
The magnesium alloy of the invention takes Bi and Sn as main alloying elements, and can form Mg with high thermal stability in situ in the alloy by controlling the content ratio of the Bi element to the Ca element2Bi2Ca phase, Mg3Bi2Phase and Mg2Sn phase, avoiding Mg2The generation of Ca phase, and the competitive growth of three alloy phases in the solidification process can inhibit the sizes of the three alloy phases, on one hand, the generation of large-size second phase is avoided, the damage to the plasticity of the alloy is reduced, and on the other hand, a proper amount of micron-sized Mg with high thermal stability is added2Bi2The Ca phase can stably exist in the heat treatment process, so that the dynamic recrystallization nucleation can be promoted and the growth of recrystallization grains can be inhibited in the extrusion process, thereby improving the quality of the alloyPlastic deformability. In addition, Bi, Sn, Ca and Y elements are simultaneously and fixedly dissolved in the alloy, so that the axial ratio of the alloy can be changed, and the mechanism of plastic deformation is further changed, thereby avoiding fiber texture and plate texture formed under the common condition, and further being beneficial to the improvement of alloy plasticity. After the alloy is subjected to solid solution and plastic processing, the tensile elongation at room temperature (25 ℃) reaches more than 35 percent.
The alloy of the invention is relatively uniform and stable during smelting, the melting point (271.3 ℃) of Bi and the melting point (231.89 ℃) of Sn which are main alloying elements are relatively low, so that the alloy melt is easily uniform, meanwhile, the comprehensive effect of Bi, Ca, Y and other alloying elements in the magnesium alloy melt is realized, the alloy melt has a relatively good flame-retardant effect, the melt is relatively stable, the casting can be completed in the air atmosphere under the condition of not higher than 760 ℃, the heat treatment can be completed in the natural atmosphere of a hearth under the condition of not higher than 450 ℃, and the good flame-retardant effect is shown.
The novel high-strength magnesium alloy only contains trace rare earth elements, and has low cost. Can be used as the material of parts of transportation, aerospace, computer, communication and consumer electronics products.
Compared with the prior art, the invention has the following remarkable improvements and advantages:
1) the magnesium alloy of the invention takes Bi element and Sn element as main alloy elements, and forms a large amount of Mg by a simple alloying method2Bi2Ca phase, Mg3Bi2Phase and Mg2Sn. Bi, Sn, Ca and Y elements which are dissolved into the matrix in the subsequent heat treatment change the axial ratio of the matrix, and under the action of extrusion processing, the texture characteristics of the morphotropic alloy are improved by the synergistic action, and meanwhile, part of Mg is also contained3Bi2Phase and Mg2Sn is dynamically separated out in a nanometer scale, so that the room temperature plasticity of the alloy is improved, and the room temperature elongation can reach more than 35%.
2) Nano-scale strengthening phase Mg in the alloy of the invention3Bi2Phase (823 ℃ C.) and Mg2Sn phase (772 deg.C) and micron-sized second phase Mg2Bi2The Ca phase has higher melting point, and the initial melting temperature of the second phase in the alloy is increased, so that the alloy isThe hot working deformation can be carried out at higher temperature, thereby reducing the resistance to thermal deformation and improving the processing or production efficiency.
3) The alloy of the invention has better flame-retardant effect in the preparation process, has more stable melt, can finish casting in the air atmosphere under the condition of not higher than 750 ℃, can finish heat treatment in the natural atmosphere of a hearth under the condition of not higher than 500 ℃, and has good flame-retardant effect.
4) The magnesium alloy does not contain any rare earth element and high-price alloy element, the metal Bi and Sn have low price, and the production cost of the alloy can be reduced (the rare earth is generally 1000-5000 yuan per kilogram, and the metal Bi and Sn used in the invention only use 100-250 yuan per kilogram);
5) the magnesium alloy has simple preparation process, breaks through the limitation of special processing modes such as large plastic deformation and the like required by most high-strength magnesium alloys, can be continuously processed and produced by the existing magnesium alloy extrusion equipment without additional improvement, and has low requirement on production equipment.
Drawings
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention will be further illustrated with reference to the accompanying drawings.
FIG. 1 is a stress-strain curve for room temperature tensile testing of the magnesium alloys of examples 1, 2, 3 and the alloy of comparative example AZ 31;
FIG. 2 is a microstructure of the alloy obtained in example 1, wherein FIG. 2a is a low power microstructure; FIG. 2b is a high magnification microstructure;
FIG. 3 is a photograph of the microstructure of the alloy obtained in example 2; wherein FIG. 3a is a macroscopic microstructure; FIG. 3b is a high magnification microstructure;
FIG. 4 is a TEM microstructure photograph of an alloy structure obtained in example 2;
FIG. 5 is a reverse pole view of the alloy obtained in example 2;
FIG. 6 is a photograph of the microstructure of the alloy obtained in example 3; wherein, FIG. 6a is a macroscopic microstructure; FIG. 6b shows a high magnification microstructure.
Detailed Description
The present invention will be further described with reference to the following specific examples and drawings, wherein the following examples are all implemented on the premise of the technical solution of the present invention, and detailed embodiments and specific procedures are provided, but the scope of the present invention is not limited to the following examples.
Three alloy compositions Mg-2.5Bi-2.5Sn-1Zr-0.4Ca-0.03Y (wt%) (alloy 1), Mg-3Bi-3Sn-1Zr-0.5Ca-0.04Y (wt%) (alloy 2), Mg-4Bi-4Sn-1Zr-0.6Ca-0.05Y (wt%) (alloy 3) were selected as typical examples.
According to the technical scheme of the invention, pure Mg (99.8 wt%) ingot, pure Bi (99 wt%) block, pure Sn (99 wt%) block, Mg-30Zr (30.01 wt% of Zr actually detected), Mg-20Ca (20.01 wt% of Ca actually detected) intermediate alloy and Mg-30Y (30.02 wt% of Y actually detected) intermediate alloy are used as alloying raw materials, and the low-cost magnesium alloy ingot is prepared by smelting; the alloy is obtained by solution treatment, peeling, pre-extrusion and cooling rolling processing. The mechanical properties of the extruded bars were measured at room temperature (25 ℃ C.) and the tensile properties of the examples and comparative examples AZ31 are shown in Table 1.
Example 1
(1) The preparation method comprises the following steps:
1) preparing materials: taking pure Mg (99.8 wt%) ingot, pure Bi (99 wt%) block, pure Sn (99 wt%) block, Mg-30Zr, Mg-20Ca and Mg-30Y intermediate alloy as raw materials, carrying out surface pretreatment (such as removing dirt, oxide skin and the like, the same in the following embodiment), and then batching according to the target components; wherein the mass ratio of Bi: ca 6.25: 1.
2) Smelting: cleaning and preheating a crucible, putting a magnesium ingot preheated to 200 ℃ into the crucible of a smelting furnace, setting the furnace temperature to be 720 ℃, and slowly heating at the heating rate of 25 ℃/min. After the molten pure Bi blocks, the pure Sn blocks, the pure Zn blocks, the Mg-30Zr intermediate alloy, the Mg-20Ca intermediate alloy and the Mg-30Y intermediate alloy which are preheated to the temperature of 50 ℃ are sequentially added into the magnesium molten liquid; raising the melting temperature to 750 ℃, preserving the temperature for 30 minutes to completely melt the alloy, then stirring for 5 minutes,introducing high-purity Ar gas (with the purity of 99.999%) into the melt, refining, degassing for 2 minutes, and then keeping the temperature and standing for 5 minutes at 750 ℃; the volume ratio of the smelting process and the heat-preservation standing process is CO2：SF6100:1 CO2：SF6Under the protection of mixed gas;
3) casting: pouring the magnesium alloy melt after standing into a cylindrical metal mold with the diameter of 60mm, preheating the mold to 250 ℃ before casting, and obtaining the as-cast magnesium alloy at the casting temperature of 750 ℃; gas protection is not needed in the casting process;
4) homogenizing: carrying out solid solution treatment on the obtained as-cast magnesium alloy, wherein the solid solution treatment temperature is 480 ℃ and the time is 10 hours, and carrying out warm water quenching at 50 ℃; gas protection is not needed in the heating and heat preservation processes of the solution treatment;
5) machining: turning to remove the oxide layer on the surface of the alloy cast ingot obtained in the step 4), and processing the alloy cast ingot into a size suitable for extrusion processing;
6) deformation processing: extruding the alloy obtained in the step 5) into a bar by using an extruder, wherein the extrusion process comprises the following main process parameters: the blank temperature is 280 ℃, the extrusion container temperature is 280 ℃, the die temperature is 280 ℃, the extrusion speed is 5m/min, the extrusion ratio is 25, the deformed blank is heated for 30 minutes to reach the required extrusion temperature of 280 ℃, and the extruded material is cooled by air cooling.
(2) Alloy performance test and microstructure analysis
The alloy obtained in the example is sampled and processed into a test bar, and a room temperature tensile test is carried out (the test of the test adopts the room temperature test method in the GB/T228.1-2010 metal material tensile test, the method is adopted in the following examples), the typical tensile curve of the magnesium alloy obtained in the example is shown in figure 1, and the tensile strength of the obtained alloy is 222.7MPa, the yield strength is 157.7MPa, and the elongation is 44.3%. (Table 1). FIG. 2 shows the microstructure of the Mg-2.5Bi-2.5Sn-1Zr-0.4Ca-0.03Y (wt%) magnesium alloy prepared in this example, and it can be seen from FIG. 2(a) that the alloy is completely recrystallized, and a small number of micron-sized second phases are randomly distributed on the substrate in the microstructure, and these second phases are mainly Mg with a higher melting point2CaBi2Phase, can promote the alloy to generate dynamic state in the extrusion processRecrystallizing; as shown in FIG. 2(b), the dynamic recrystallization grain size is about 8 to 30 μm, and fine precipitates, which are Mg produced by dynamic precipitation of Bi and Sn elements dissolved in a matrix during extrusion, exist in the alloy3Bi2Phase and Mg2The Sn phase can inhibit the twinning of the alloy in the deformation process at room temperature from occurring in advance, thereby improving the plasticity of the alloy.
Example 2
(1) The Mg-3Bi-3Sn-1Zr-0.5Ca-0.04Y (wt%) alloy component is designed and selected to be matched into the magnesium alloy, and the preparation method comprises the following steps:
1) preparing materials: taking pure Mg (99.8 wt%) ingot, pure Bi (99 wt%) block, pure Sn (99 wt%) block, Mg-30Zr, Mg-20Ca and Mg-30Y intermediate alloy as raw materials, carrying out surface pretreatment (such as removing dirt, oxide skin and the like, the same in the following embodiment), and then batching according to the target components; the mass ratio Bi: ca 6: 1.
2) Smelting: cleaning and preheating a crucible, putting a magnesium ingot preheated to 200 ℃ into the crucible of a smelting furnace, setting the furnace temperature to be 720 ℃, and slowly heating at the heating rate of 25 ℃/min. After the molten pure Bi blocks, the pure Sn blocks, the pure Zn blocks, the Mg-30Zr intermediate alloy, the Mg-20Ca intermediate alloy and the Mg-30Y intermediate alloy which are preheated to the temperature of 50 ℃ are sequentially added into the magnesium molten liquid; raising the smelting temperature to 750 ℃, preserving heat for 30 minutes to completely melt the alloy, then stirring for 5 minutes, introducing high-purity Ar gas into the melt to carry out refining degassing treatment for 2 minutes, preserving heat and standing at 750 ℃ for more than 5 minutes, wherein the volume ratio of the smelting process and the heat preservation standing process is CO2：SF6100:1 CO2：SF6Under the protection of mixed gas;
3) casting: pouring the magnesium alloy melt after standing into a cylindrical metal mold with the diameter of 60mm, preheating the mold to 250 ℃ before casting, and obtaining the as-cast magnesium alloy at the casting temperature of 750 ℃; gas protection is not needed in the casting process;
4) homogenizing: carrying out solid solution treatment on the obtained as-cast magnesium alloy, wherein the solid solution treatment temperature is 480 ℃ and the time is 10 hours, and carrying out warm water quenching at 50 ℃; gas protection is not needed in the heating and heat preservation processes of the solution treatment;
5) machining: turning to remove the oxide layer on the surface of the alloy cast ingot obtained in the step 4), and processing the alloy cast ingot into a size suitable for extrusion processing;
6) deformation processing: extruding the alloy obtained in the step 5) into a bar by using an extruder, wherein the extrusion process comprises the following main process parameters: the blank temperature is 280 ℃, the extrusion container temperature is 280 ℃, the die temperature is 280 ℃, the extrusion speed is 5m/min, the extrusion ratio is 25, the deformed blank is heated for 30 minutes to reach the required extrusion temperature of 280 ℃, and the extruded material is cooled by air cooling.
(2) Alloy performance test and microstructure analysis
The alloy obtained in this example was sampled and processed into test bars and subjected to a room temperature tensile test, and a typical tensile curve of the magnesium alloy obtained in this example is shown in fig. 1, and it was found that the tensile strength of the alloy obtained was 238.3MPa, the yield strength was 176MPa, and the elongation was 39.1%. (Table 1). FIG. 3 shows the microstructure morphology of the Mg-3Bi-3Sn-1Zr-0.5Ca-0.04Y (wt%) magnesium alloy prepared in this example, and it can be seen from FIG. 3(a) that the alloy is completely recrystallized, and a small amount of micron-sized second phases are randomly distributed on the substrate in the microstructure, and these second phases are mainly Mg with a higher melting point2CaBi2The phase can promote the dynamic recrystallization of the alloy during the extrusion process; as shown in FIG. 3(b), the dynamic recrystallization grain size is about 25 μm, and fine precipitates, which are Mg produced by dynamic precipitation of Bi and Sn elements dissolved in a matrix during extrusion, exist in the alloy3Bi2Phase and Mg2The Sn phase can inhibit the twinning of the alloy in the deformation process at room temperature from occurring in advance, thereby improving the plasticity of the alloy. To further observe the dynamic precipitation, fig. 4 shows the TEM structure of alloy 2, from which it can be seen that there are a large number of micron-sized precipitates and fine nanometer-sized dynamic precipitates of different sizes in the alloy, consistent with the observation of fig. 3. FIG. 5 is a reversed pole diagram of alloy 2, which shows that the alloy has non-basal plane texture and the texture has low strength, and shows that the alloy breaks through the constraint of the basal plane texture generated by the traditional alloy after extrusion, and can greatly improveGood room temperature plasticity of alloy.
Example 3
(1) The preparation method comprises the following steps:
1) preparing materials: taking pure Mg (99.8 wt%) ingot, pure Bi (99 wt%) block, pure Sn (99 wt%) block, Mg-30Zr, Mg-20Ca and Mg-30Y intermediate alloy as raw materials, carrying out surface pretreatment (such as removing dirt, oxide skin and the like, the same in the following embodiment), and then batching according to the target components; the mass ratio Bi: ca 6.67: 1.
2) Smelting: cleaning and preheating a crucible, putting a magnesium ingot preheated to 200 ℃ into the crucible of a smelting furnace, setting the furnace temperature to be 720 ℃, and slowly heating at the heating rate of 25 ℃/min. After the molten pure Bi blocks, the pure Sn blocks, the pure Zn blocks, the Mg-30Zr intermediate alloy, the Mg-20Ca intermediate alloy and the Mg-30Y intermediate alloy which are preheated to the temperature of 50 ℃ are sequentially added into the magnesium molten liquid; raising the smelting temperature to 750 ℃, preserving heat for 30 minutes to completely melt the alloy, then stirring for 5 minutes, introducing high-purity Ar gas into the melt to carry out refining degassing treatment for 2 minutes, preserving heat and standing at 750 ℃ for more than 5 minutes, wherein the volume ratio of the smelting process and the heat preservation standing process is CO2：SF6100:1 CO2：SF6Under the protection of mixed gas;
3) casting: pouring the magnesium alloy melt after standing into a cylindrical metal mold with the diameter of 60mm, preheating the mold to 250 ℃ before casting, and obtaining the as-cast magnesium alloy at the casting temperature of 750 ℃; gas protection is not needed in the casting process;
4) homogenizing: carrying out solid solution treatment on the obtained as-cast magnesium alloy, wherein the solid solution treatment temperature is 480 ℃ and the time is 10 hours, and carrying out warm water quenching at 50 ℃; gas protection is not needed in the heating and heat preservation processes of the solution treatment;
5) machining: turning to remove the oxide layer on the surface of the alloy cast ingot obtained in the step 4), and processing the alloy cast ingot into a size suitable for extrusion processing;
6) deformation processing: extruding the alloy obtained in the step 5) into a bar by using an extruder, wherein the extrusion process comprises the following main process parameters: the blank temperature is 280 ℃, the extrusion container temperature is 280 ℃, the die temperature is 280 ℃, the extrusion speed is 5m/min, the extrusion ratio is 25, the deformed blank is heated for 30 minutes to reach the required extrusion temperature of 280 ℃, and the extruded material is cooled by air cooling.
(2) Alloy performance test and microstructure analysis
The alloy obtained in this example was sampled and processed into test bars and subjected to a room temperature tensile test, and a typical tensile curve of the magnesium alloy obtained in this example is shown in fig. 1, and it was found that the tensile strength of the alloy obtained was 246.7MPa, the yield strength was 188.4MPa, and the elongation was 35.7%. (Table 1). FIG. 6 shows the microstructure of the Mg-4Bi-4Sn-1Zr-0.6Ca-0.05Y (wt%) magnesium alloy prepared in this example, and it can be seen from FIG. 6(a) that the alloy is completely recrystallized, and a small amount of micron-sized second phases are randomly distributed on the substrate in the structure, and these second phases are mainly Mg with a higher melting point2CaBi2The phase can promote the dynamic recrystallization of the alloy during the extrusion process; as shown in FIG. 6(b), the dynamic recrystallization grain size is about 28 μm, and fine precipitates, which are Mg produced by dynamic precipitation of Bi and Sn elements dissolved in a matrix during extrusion, exist in the alloy3Bi2Phase and Mg2The Sn phase can inhibit the twinning of the alloy in the deformation process at room temperature from occurring in advance, thereby improving the plasticity of the alloy. As can be seen from fig. 6(a) and (b), the alloy microstructure of this example is similar to the alloy microstructures of example 1 and example 2.
In summary, the alloy of the invention firstly introduces Sn element on the basis of Mg-Bi alloy, and carries out multi-element trace composite alloying with trace Zr, Ca and Y elements, thereby forming texture (structure) configuration with non-basal texture in the alloy and preparing the alloy material with excellent room temperature plasticity. Secondly, the content and the proportion of Bi element and Ca element in the alloy of the invention are limited to a certain extent and controlled between 7:1 and 6:1, thereby avoiding Mg2Ca phase is generated to avoid the deterioration of the plasticity of the alloy.
In the preparation method of the alloy, firstly, the alloy can be directly cast in the atmosphere without protection of protective gas in the casting and heat treatment processes, and most of other magnesium alloys need to be cast and heat treated under the protection of vacuum or protective gas; this is also an indication that the alloy has certain flame retardant properties. ② the smelting and heat preservation need to be carried out at a higher temperature (750 ℃) in the smelting process.
Comparative example
Selecting a current commercial magnesium alloy, AZ31 magnesium alloy, and comprising the following components: mg-2.9Al-0.75Zn-0.3Mn (wt%) was used as a comparative example. A typical stress-strain curve of a comparative example (obtained under the same processing conditions as example 2) in a tensile test is shown in fig. 1. The tensile strength was 223.7MPa, the yield strength was 203.5MPa, and the elongation was 20.2% (Table 1).
The comparison shows that the elongation percentage of the novel magnesium alloy is similar to that of the comparative example, the tensile strength and the yield strength are greatly improved, the strength is greatly higher than that of the current commercial high-strength magnesium alloy, the effect similar to that of the alloy added with a large amount of rare earth elements and Li elements is achieved, and the novel magnesium alloy is a novel room-temperature high-plasticity magnesium alloy with great market competitiveness. This is mainly due to the combined effect of the change of alloy texture and the existence of nano precipitated phase.
TABLE 1 results of mechanical properties at room temperature for examples and comparative examples
Figure BDA0001870718710000081
The raw materials and equipment used in the above examples are obtained by known means, and the procedures used are within the skill of those in the art.
The invention is not the best known technology.

Claims (7)

1. The low-cost high-room-temperature plastic deformation magnesium alloy is characterized in that the alloy is Mg-Bi-Sn-Zr-Ca-Y alloy, and the mass percent of the chemical components of the alloy is as follows: 2-5.0 wt% of Bi; 2-5.0 wt% of Sn; 0.5-1.2 wt% of Zr; 0.1-0.8 wt% of Ca; 0.01 to 0.08 wt% of Y, and the balance of Mg and inevitable impurities; and, the mass ratio Bi: ca is 6-7: 1;
the preparation method of the low-cost high-room-temperature plastic deformation magnesium alloy comprises the following steps of:
1) preparing materials: taking pure Mg ingot, pure Bi block, pure Sn block, Mg-Zr intermediate alloy, Mg-Ca intermediate alloy and Mg-Y intermediate alloy as raw materials, and batching according to the components of the magnesium alloy;
2) smelting: putting a pure Mg ingot into a crucible of a smelting furnace, setting the furnace temperature to 700-730 ℃ and keeping the furnace temperature, and after the pure Mg ingot is melted, respectively adding a pure Bi block and a pure Sn block which are preheated to 50-80 ℃, and a Mg-Zr intermediate alloy, a Mg-Ca intermediate alloy and a Mg-Y intermediate alloy which are preheated to 100-150 ℃ into a magnesium solution; then raising the melting temperature to 750-780 ℃, preserving the heat for 10-30 minutes until the alloy is molten, stirring for 3-10 minutes, and introducing high-purity Ar gas into the melt for refining and degassing treatment; regulating and controlling the temperature to 750-760 ℃, and keeping the temperature and standing for 3-10 minutes; the smelting and the heat preservation standing processes are both in CO2/SF6Under the protection of mixed gas;
3) casting: pouring the magnesium alloy melt after standing into a mold preheated to 200-250 ℃ to prepare as-cast magnesium alloy; gas protection is not needed in the casting process;
4) solid solution: carrying out solid solution treatment on the obtained as-cast magnesium alloy, wherein the solid solution treatment temperature is 460-500 ℃ and the time is 8-12 hours, and then quenching with warm water at the temperature of 30-80 ℃; gas protection is not needed in the heating and heat preservation processes of the solution treatment;
5) cutting the cast ingot subjected to the solution treatment obtained in the previous step into corresponding blanks and peeling;
6) extrusion deformation: heating the blank obtained in the previous step to 270-400 ℃ within 20-30 minutes, and then putting the blank into a die for deformation processing; and air cooling is carried out after the deformation processing, and finally the magnesium alloy material with low cost and high room temperature plastic deformation is obtained.
2. The low-cost high-room-temperature plastically deformable magnesium alloy according to claim 1, wherein in said production method, the die is a die for forming a bar, a plate, a pipe, a wire or a shape.
3. The low-cost high-room-temperature plastically deformable magnesium alloy according to claim 1, wherein in the preparation method, the stirring in the step 2) is mechanical stirring or argon-blowing stirring.
4. The low-cost high-room-temperature plastically deformable magnesium alloy according to claim 1, wherein in said production method, the Mg-Zr intermediate alloy is Mg-30Zr intermediate alloy.
5. The low-cost high-room-temperature plastically deformable magnesium alloy as claimed in claim 1, wherein in said production method, the Mg-Ca master alloy is Mg-20Ca master alloy.
6. The low-cost high-room-temperature plastically deformable magnesium alloy as claimed in claim 1, wherein in said production method, the Mg-Y master alloy is Mg-30Y master alloy.
7. The low-cost high-room-temperature plastically deformable magnesium alloy as claimed in claim 1, wherein in said production method, CO2And SF6The mixed gas of (A) is composed of CO in a volume ratio2：SF6＝50～100：1。
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